U.S. patent number 4,420,388 [Application Number 06/301,754] was granted by the patent office on 1983-12-13 for hydrotreating vacuum gas oils with catalyst and added organic fluorine compound.
This patent grant is currently assigned to Standard Oil Company (Indiana). Invention is credited to Ralph J. Bertolacini, James F. Mosby, John G. Schwartz.
United States Patent |
4,420,388 |
Bertolacini , et
al. |
December 13, 1983 |
Hydrotreating vacuum gas oils with catalyst and added organic
fluorine compound
Abstract
The method of converting at least 20% by weight of a vacuum gas
oil fraction boiling above 650.degree. F. into products having a
boiling point less than about 650.degree. F., which comprises
hydrotreating a vacuum gas oil with a hydrodesulfurization catalyst
comprising a Group VIB and Group VIII metal wherein an organic
fluorine compound is added to the vacuum gas oil during
hydrotreating and the vacuum gas oil is hydrotreated under hydrogen
at a temperature of at least 740.degree. F.
Inventors: |
Bertolacini; Ralph J.
(Naperville, IL), Mosby; James F. (Palos Heights, IL),
Schwartz; John G. (Naperville, IL) |
Assignee: |
Standard Oil Company (Indiana)
(Chicago, IL)
|
Family
ID: |
23164719 |
Appl.
No.: |
06/301,754 |
Filed: |
September 14, 1981 |
Current U.S.
Class: |
208/112;
208/216R |
Current CPC
Class: |
C10G
45/08 (20130101); C10G 2400/06 (20130101) |
Current International
Class: |
C10G
45/02 (20060101); C10G 47/00 (20060101); C10G
45/08 (20060101); C10G 49/00 (20060101); C10G
47/12 (20060101); C10G 047/12 () |
Field of
Search: |
;208/112,216R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Garvin; Patrick
Assistant Examiner: Chaudhuri; O.
Attorney, Agent or Firm: Magidson; William H. McClain;
William T.
Claims
We claim:
1. The method of hydrotreating which comprises converting at least
20 percent by weight of a vacuum gas oil fraction boiling above
650.degree. F. into products having a boiling point less than about
650.degree. F. with a hydrodesulfurization catalyst comprising a
Group VIB and Group VIII metal on a support consisting essentially
of alumina wherein an organic fluorine compound is added to the
vacuum gas oil during hydrotreating and the vacuum gas oil is
hydrotreated under hydrogen at a temperature of at least
740.degree. F.
2. The process of claim 1 wherein the Group VIB metal is molybdenum
and the Group VIII metal is cobalt or nickel.
3. The process of claim 2 wherein hydrotreating is carried out at a
temperature of about 740.degree. F. to 800.degree. F.
4. The process of claim 3 wherein the vacuum gas oil contains at
least 0.5 percent by weight sulfur.
5. The method of hydrotreating which comprises converting at least
20 percent by weight of a vacuum gas oil fraction boiling above
650.degree. F. into products having a boiling point less than about
650.degree. F. which comprises hydrotreating a vacuum gas oil
having at least a 0.5 percent by weight sulfur with a
hydrodesulfurization catalyst comprising cobalt and molybdenum on a
support consisting essentially of refractory alumina wherein an
organo-fluorine compound is added to the vacuum gas oil and said
vacuum gas oil is hydrotreated under hydrogen at a temperature of
at least 740.degree. F.
6. The process of claim 5 wherein sufficient organo-fluorine
compound is added to provide the catalyst with 0.5 to 6 percent by
weight fluoride and the vacuum gas oil is hydrotreated under
hydrogen at a temperature of 740.degree. to 800.degree. F.
7. The process of claim 1 wherein said support is alumina.
Description
This invention relates to hydrotreating vacuum gas oils containing
at least 0.5% by weight sulfur with a hydrodesulfurization catalyst
wherein an organo-fluorine compound is added on stream to the
vacuum gas oil feed and the vacuum gas oil is hydrotreated under
hydrogen at a temperature of at least 740.degree. F.
In the last few years, it has become necessary to process oils
containing higher and higher levels of sulfur. At the same time,
environmental rules have placed more stringent limitations on the
amount of sulfur that can be emitted into the air. In many
refineries, low sulfur vacuum gas oils are hydrodesulfurized to a
relatively low sulfur content and conveyed to a cracking unit, such
as a fluidized catalytic cracker. When a low sulfur vacuum gas oil
is employed, a relatively high percentage of the sulfur is removed
from the vacuum gas oil before the hydrotreated product is cracked.
Even in these cases, an undesirable level of SO.sub.x can be
emitted from the cracking units. This has led to numerous schemes
and additives for converting the SO.sub.x to H.sub.2 S which can be
handled readily in sulfur recovery units attached to hydrotreating
units and cracking units. As the level of sulfur in the vacuum gas
oil increases, there is less complete conversion of sulfur to
H.sub.2 S in the hydrotreating units and a commensurately higher
load of SO.sub.x produced in the cracking units. For example, it is
not unusual when processing a vacuum gas oil containing 3% sulfur
in conventional hydrotreating units to remove only 90% of the
sulfur. However, this is not satisfactory today. Since some
refineries lack cracking facilities or have insufficient cracking
capacity for processing all the hydrodesulfurized vaccum gas oil
produced, substantially complete removal of sulfur from gas oils
during hydrodesulfurization is even more important. Accordingly,
there is a need for more efficient methods of reducing the level of
sulfur in vacuum gas oils.
As indicated above, some refineries do not have adequate cracking
facilities for treating all hydrodesulfurized gas oil. Accordingly,
the product slate produced by hydrodesulfurization is critical to
the economic viability of the refinery. It is important that these
refineries have means of converting the hydrodesulfurized gas oils
into large volume products boiling below 650.degree. F., such as,
gasoline or middle distillates. Unfortunately, hydrodesulfurization
produces very little gasoline or middle distillates since there is
less than 10% conversion of the 650+.degree. F. fraction.
Therefore, there is a need for hydrodesulfurization processes that
produce substantially higher levels of gasoline and middle
distillates, preferably middle distillates boiling below
650.degree. F. High volumes of middle distillates are desirable
since they can be utilized for diesel fuel.
It is well known that hydrodesulfurization catalysts have optimum
temperature ranges to accomplish the desired result. For example,
the conventional cobalt-molybdenum and nickel-molybdenum
hydrodesulfurization catalysts are generally employed at a
temperature of around 700.degree. F. If one carries out
hydrodesulfurization with these molybdenum catalysts at higher
temperatures, such as 740.degree. F., the catalysts deactivate
rapidly. Accordingly, it is not possible to obtain greater
conversion of the 650+.degree. F. by raising the treating
temperature of the vacuum gas oil.
Numerous patents describe the use of halogen promoters for the
treatment of petroleum streams. Some of these patents describe the
treatment of various hydroprocessing catalysts with halogens such
as a chlorine and fluorine. In other cases, organic halogen
compounds, preferably carbon tetrachloride, have been added to the
hydrocarbon stream being treated. In most cases the patentees
desire to avoid the conversion of the hydrocarbon stream into
low-boiling gaseous materials.
Sze U.S. Pat. No. 4,181,601 discloses a process of producing light
olefins, benzene, toluene and xylenes wherein a halogenated
bimetallic catalyst is employed to hydrotreat gas oils without
excessive hydrocracking and gas production at a temperature of
about 640.degree. F. to 950.degree. F. followed by thermal
cracking. The patentee indicates that there are increased yields of
light olefins, benzene, toluene and xylene ensuing from the use of
the halogenated catalyst in the first step of the two step process.
While the patentee indicates that either chlorine or fluorine
substituted organic compounds can be employed to halogenate the
catalyst on stream, all of the examples in the patent utilize
organic chlorine compounds. Further, while the patentee indicates
that the hydrogenation can be carried out at 640.degree. F. to
950.degree. F., preferably 650.degree. F. to 750.degree. F., all of
the examples employ a temperature in the range of about 690.degree.
F. to 700.degree. F. The patentee fails to appreciate the fact that
the use of an organic fluorine compound plus a higher temperature
in the range of about 740.degree. F. to 800.degree. F. results in
advantageous hydrocracking of the fraction of the gas oils boiling
at more than 650.degree. F. without the formation of undesirable
gaseous products.
Michelson U.S. Pat. No. 4,220,557 discloses the fluoriding of
hydrodesulfurization catalysts with fluorosilicates. While the
patentee indicates that these catalysts can be advantageously used
for the hydrogenation and cracking of organic sulfur and nitrogen
compounds in hydrocarbon feedstocks, including light and heavy gas
oils, at a temperature of 450.degree. F. to 900.degree. F.,
preferably 550.degree. F. to 800.degree. F., the patentee's sole
example is directed to hydrodesulfurization of a light diesel fuel
boiling between 400.degree. F. and 650.degree. F. with the
hydrodesulfurization being carried out at 700.degree. F. However,
the patentee fails to recognize that it is possible to convert a
substantial portion of the 650+.degree. F. fraction of vacuum gas
oils to middle distillates by treatment at approximately
740.degree. F. to 780.degree. F. with on stream fluoriding of the
catalyst.
The general object of this invention is to provide a process of
hydrotreating relatively high sulfur vacuum gas oils under
conditions wherein substantially all of the sulfur contained in the
vacuum gas oil is converted to H.sub.2 S and wherein approximately
20 to 50% by weight or more of the vacuum gas oil fraction boiling
above 650.degree. F. is converted into products having a boiling
point less than about 650.degree. F. without the formation of
excessive quantities of low molecular weight gaseous hydrocarbons,
such as ethane, propane, etc. Other objects appear hereinafter.
We have now found that the objects of this invention can be
attained by hydrotreating vacuum gas oils containing at least 0.5%
sulfur, preferably at least 1% sulfur, with a hydrodesulfurization
catalyst wherein an organic fluoride compound is added to the
vacuum gas oil feed during hydrotreating and the vacuum gas oil is
hydrotreated under hydrogen at a temperature of at least
740.degree. F. Our studies have shown that there is relatively
little hydrocracking of the vacuum gas oil unless the vacuum gas
oil is heated to at least 740.degree. F. with cobalt-molybdenum
catalyst. Further, hydrocracking does not start until such time as
substantially all of the sulfur in the feedstock capable of being
removed at 740.degree. F. has been removed. When prior art
processes are carried out at about 700.degree. F. without on stream
fluoriding using a vacuum gas oil containing 3% by weight sulfur
(1) only about 90% of the sulfur is removed and (2) there is less
than 10% conversion of the fraction boiling at above 650.degree. F.
Other things being equal when the process of this invention is
employed there is 99% removal of sulfur and over 20% conversion of
the fraction boiling at above 650.degree. F. into desirable
non-gaseous products.
Although the organo-fluorine compound can be added continuously to
the hydrocarbon stream, it is generally preferable to add a
sufficient concentration of organo-fluorine compound to the
hydrocarbon stream to raise the level of fluorine on the catalyst
to about 0.5 to 6% by weight and then operate the hydrocracker for
several weeks without replenishment of the organo-fluorine
compound. The instant process has the additional advantage that it
is possible to operate the unit as a hydrotreater without any
substantial hydrocracking by allowing the fluorine to dissipate
during use. The unit can be operated as a hydrocracker again by
replenishing the organo-fluorine compound from time to time.
Briefly, this invention comprises hydrotreating vacuum gas oils
containing at least 0.5% by weight sulfur, preferably at least 1%
by weight sulfur, with a hydrodesulfurization catalyst comprising a
Group VIB metal and Group VIII metal wherein an organic fluoride
compound is added to the vacuum gas oil feed during hydrotreating
and the vacuum gas oil is hydrotreated under hydrogen at a
temperature of at least 740.degree. F.
As indicated above, vacuum gas oils useful in this invention
contain at least 0.5% by weight sulfur, preferably at least 1% by
weight sulfur. While substantially any vacuum gas oil can be used
in this invention, the process is particularly useful for
hydrodesulfurization of vacuum gas oils having a substantial
quantity of sulfur. For example, the process of this invention can
be utilized to remove approximately 99% by weight of the sulfur
contained in a vacuum gas oil having 3% by weight sulfur.
The catalyst useful in this invention is a bimetallic catalyst
comprising at least one metal from Group VIB and at least one metal
from Group VIII of the periodic table. The Group VIB metal is
generally molybdenum and the Group VIII metal is generally nickel
and/or cobalt. The active form of the catalyst is the sulfided form
and such sulfiding can be effected prior to the use of the
catalyst, or in situ, since the gas oil feed contains sulfur. The
catalyst can be supported on any of the supports normally used in
this art, such as, alumina; alumina-silica; alumina-silica
containing zeolites; alumina-magnesia, etc. The various Group VIB
and Group VIII metals can be used in the concentrations normally
employed in this art.
The organic fluorine compounds include carbon tetrafluoride;
difluoroethane, fluorobenzene, etc. As indicated above, the
fluorine component apparently reacts with the support to provide
hydrocracking activity to the catalyst. Further, the fluorine
component acts as a stabilizer for the catalyst in the sense that
it permits the catalyst to be utilized at a higher temperature
without deactivation of the catalyst. For example, whereas typical
molybdenum/Group VIII catalysts deactivate at a temperature of
about 740.degree. F. and higher, the fluorided catalysts utilized
in this invention function effectively as hydrocracking catalysts
at a temperature range of about 740.degree. F. to 800.degree. F.
without deactivation. The catalysts can be pretreated with any
fluorine containing compound, such as organo-fluorine compounds or
inorganic fluorine compounds prior to use. However, the preferred
procedure is to treat the catalyst in situ with a
fluoro-substituted hydrocarbon in the vacuum gas oil feedstock.
Irrespective of the fluoriding method, sufficient fluorine
containing compound should be reacted with the catalyst to increase
its weight by 0.5 to 6%. Further, it is essential for the purpose
of this invention that organo-fluorine compound be supplied to the
catalyst from time to time to maintain hydrocracking activity and
stabilizing effect on the catalyst. Under these circumstances, the
fluorine containing compound is supplied as an organo-compound
which decomposes on contact with the catalyst. The orgao-fluorine
containing compounds have the advantage that there is less of a
tendency for degradation of the reactor walls due to the formation
of hydrofluoric acid.
Hydrogenation is effected at a temperature of at least 740.degree.
F., e.g. 740.degree.-800.degree. F. Other things being equal, the
higher the reaction temperature, the greater the conversion of the
650+.degree. F. fraction of the gas oil into 650-.degree. F.
material. For example, at about 740.degree. F., there is at least
20% conversion of the 650+.degree. F. fraction, whereas at about
780.degree. F., there is approximately 50% conversion of the
650+.degree. F. fraction. The maximum temperature is dependent on
the metallurgical limits of the reactor. The hydrodesulfurization
reaction is carried out under hydrogen using a sufficient
concentration of hydrogen to effect efficient hydrotreating and
hydrocracking of the vacuum gas oil. In general, hydrogen can be
employed in a concentration of 1,000 to 15,000 SCF per barrel. The
liquid hourly space velocity can range from about 0.5 to 3.40.
EXAMPLE I
A Kuwait heavy vacuum gas oil having a gravity of 22.8.degree. API,
3.01 percent by weight sulfur, 0.09 percent nitrogen, 4.9 percent
by weight fraction boiling between 360.degree. to 650.degree. F.
and 95.1 percent by weight fraction boiling at 650+.degree. F. was
hydrotreated in an isothermal bench-scale, trickle-bed reactor
using once-through hydrogen. The reactor had a nominal inside
diameter of 0.546", a thermowell with a nominal outside diameter of
0.125" which passed axially through the catalyst bed. Eurotherm
temperature controls were used to maintain an isothermal
(.+-.3.degree. F.) reactor bed temperature by means of electrical
heaters around the top, middle and bottom sections of the reactor.
The 33.5 cc catalyst bed was 9.2" in length and was loaded into the
middle heating zone with the oil delivered to the reactor by a
Ruska pump together with hydrogen. The 2-phase reactant mixture
(oil and hydrogen) passed vertically downward through the catalyst
bed comprising a sulfided commercial 1/16" cobalt-molybdenum on
alumina extrudate. The products were then passed into a separator
with the flow of liquid product being controlled by a level control
valve. The conditions of reaction over a 27 day period are set
forth below in Table I. The catalyst was fluorided over the period
of days 8 to 9 and again at day 21 by adding difluoroethane in
liquid naphtha from a second Ruska pump to the gas oil.
Fluoridation at days 8 and 9 was continued until the catalyst had a
weight gain of approximately 3 percent by weight fluoride.
Fluoridation at day 21 was continued until the fluoride level was
approximately 3 percent by weight. Table I also indicates the
sulfur content of the treated gas oil and the extent of conversion
of the 650+.degree. F. fraction of the vacuum gas oil.
TABLE I ______________________________________ Wt. % Days 650 +
.degree.F. Wt. % on Tempera- LHSV Wt. % Conver- Desulfur- Oil ture
.degree.F. Vo/Hr/Vc Sulfur sion ization
______________________________________ 1 650 1.68 1.62 3.07 47.04 2
650 1.68 1.63 2.35 46.91 3 650 1.68 1.61 4.28 47.31 4 700 1.68 0.96
6.97 68.73 5 700 1.68 0.85 6.70 72.34 6 700 1.68 0.87 6.58 71.66 7
700 1.68 0.90 6.72 70.72 8 650 1.80 1.30 4.83 57.50 9 650 1.80 1.48
3.97 51.67 10 700 1.68 0.90 5.08 70.74 11 700 1.68 0.74 5.43 75.95
12 700 1.68 0.80 5.60 74.01 13 700 1.68 0.74 6.09 75.99 14 700 1.68
0.70 5.61 77.21 15 739 1.68 0.33 10.03 89.36 16 740 1.68 0.29 12.45
90.64 17 740 1.68 0.30 13.31 90.31 18 741 0.45 0.02 29.24 99.37 19
741 0.45 0.09 24.78 97.14 20 740 0.45 0.02 26.71 99.26 21 650 0.45
0.28 11.51 90.91 22 740 0.45 0.05 27.96 98.40 23 740 0.45 0.02
30.22 99.39 24 740 0.45 0.02 30.85 99.37 25 740 0.45 0.01 29.48
99.58 26 740 0.45 0.01 31.26 99.65 27 740 0.45 0.01 29.84 99.61
______________________________________
The above Table clearly shows that there is no substantial
conversion of 650+.degree. F. material until the catalyst is
fluorided and the reaction temperature is raised to about
740.degree. F. Further, the above data clearly shows it is possible
to remove in excess of 99% by weight of the sulfur contained in the
vacuum gas oil. In days 18 through 27 when the process was operated
at about 740.degree. F. using a fluorided catalyst, there was in
excess of 20% by weight conversion of the 650+.degree. F. fraction
of the vacuum gas oil.
EXAMPLE II
When the process described in Example I was carried out at
approximately 760.degree. F. for a ten day period after fluoriding,
the average degree of conversion of the 650+.degree. F. fraction of
the vacuum gas oil was approximately 35% and desulfurization was at
least 99.4%.
EXAMPLE III
When the process described in Example I was repeated at a
temperature of about 780.degree. F. for a period of ten days after
fluoriding, the average degree of conversion of the 650+.degree. F.
fraction of the vacuum gas oil was about 48% and desulfurization
was at least 99.5% by weight.
* * * * *